Schering-Plough has been boosted by data from a mid-stage study of its new anti-platelet agent which has shown promise in not increasing the risk of bleeding.

Results from a Phase II trial of SCH 530348, a novel oral thrombin receptor antagonist, have been published in The Lancet. These demonstrate that the compound met its primary endpoints of safety and tolerability.

Specifically the data show that TRA showed no increase in bleeding when given with current standard antiplatelet therapy, ie aspirin and Sanofi-Aventis/Bristol-Myers Squibb’s Plavix (clopidogrel) for patients undergoing percutaneous coronary intervention (PCI), also known as balloon angioplasty with stenting. Participants in the 1,030-patient trial were divided into groups that received one of three doses of TRA (10mg, 20mg or 40mg) or placebo.

Those patients who subsequently underwent PCI (573 of them) were randomised to one of three daily maintenance doses of TRA (0.5mg, 1.0mg, 2.5mg) plus aspirin and clopidogrel. Patients on placebos also took aspirin and Plavix alone.

The study found that the incidence of major and minor bleeding was 3% in both the collective TRA treatment arms and the current standard care alone arm. S-P also noted that although not statistically significant, the incidence of death or major adverse cardiac event at 60 days was 9% in the placebo group compared with 6% across all TRA dosages.

Richard Becker, director of the Duke Cardiovascular Thrombosis Center and lead author of the study, said the results are encouraging “as they support the viability of TRA as a potential new antiplatelet therapy option." He added that the drug “appears to work in a novel way that is complementary to current antiplatelet therapies".

S-P, which earlier this week agreed to merge with Merck & Co, is currently studying TRA in two large Phase III trials, one in patients with stroke and peripheral arterial disease, and the other whose participants suffer from acute coronary syndrome. SCH 530348 has been granted fast-track status by the US Food and Drug Administration and is viewed by analysts as a potential blockbuster.